¿Tener o Soy?
Its confussing to work out the difference between the ´tener o ser´
por ejemplo...
Tengo quince años (I am fifteen years old) Tengo frío (I am cold)
Soy alto (I am tall) Soy ....
Thanks 
8 Answers
I am fifteen years old
Well, let's see "fifteen years old", a measure of time/age. So that's what you are? A measure of time? Not a human being, boy, girl, student, adult but a measure of time?
Perhaps you mean, you've been alive for fifteen years or you were born fifteen years ago or have fifteen years "under your belt".
You don't sound confused as you used them all correctly. The tener periphrases must just be learned as there is no obvious reason why the (I am) is rendered as soy in some cases and tengo in others. It just the nature of the beast.
You could observe that the Tener expresssions or more temporary conditions than the Ser conditions. Being hungry, cold, lucky, sleepy, a certain age, etc. are all rather transitory states while the Ser are more permanent, inherent qualities, but that argument doesn't hold up between Ser and Estar so I would imagine it doesn't here either and exceptions would exist.
Its confussing to work out the difference between the ´tener o ser´
The difference is that those two verbs cannot be mapped to English verbs -the meanings and usages are too different.
"Ser" is mainly used to define and identify things and people. You don't define yourself as a "XXXX y.o." type of person, so that excludes the use of this verb with ages (it has other uses, but that's another story). "Tener" broadly translates as "to have" in the sense of "to own", but it has numerous uses that neither "have" nor "own" accept, and while they make sense in Spanish, they don't in English. We say "Tengo sueño", whose literal translation would be something like "I have a sleepy feeling/sleepiness", but the proper translation is "I am sleepy". Why using "tener" (to have) and not "to be" like in "I'm sleepy"? Well, "drowsiness" is a very close concept, and "to have drowsiness" can be used along with "to be drowsy", so why don't you say "to have sleepiness" along with "to be sleepy"?
Do not translate literally from English to Spanish . While it may work with many sentences, chances are you will end up producing about 10-40% of inadmissible garbage most of the time depending on the type of sentences. "Change your mind" may sound like a drastic surgical brain operation in Spanish, and "I am hot" will be sound in Spain as if you are trying to have sex like mad. You have to learn Spanish from natives before you can use it.
What Qfreed said. The tener phrases you used don't mean I am, they mean I have. The difference is that in Spanish you don't say I am fifteen years old or I am cold, you say I have fifteen years and I have cold. Why? Why not? Why does English say it the other way?
You can't translate the words, you have to translate the meaning.
I understand translations are useless. But how will we know what's being said without a translation? Just guess or use context clues?
Change your mind" may sound like a drastic surgical brain operation in Spanish, and "I am hot" will be sound in Spain as if you are trying to have sex like mad. You have to learn Spanish from natives before you can use it.
If thats bad, wait untill someone tries to translate these lyrics from Spains most popular recent song.
"Quiero tener tu fragancia conmigo, Y beberme de ti lo prohibido."
If you think this is confusing, wait untill you get to the difference between soy and estoy.
Nah just kidding, its not that bad.
This is one example why I think it's important to learn Spanish from a cultural perspective. The way some things are expressed in English make absolutely no sense to me, especially since I've been learning Spanish, which seems to make a lot of sense.
